The US has some 8,400 troops in Afghanistan with about another 5,000 from NATO allies, mostly taking part in the training mission.

US Marines returned to Afghanistan's volatile Helmand Saturday, where American troops faced heated fighting until NATO's combat mission ended in 2014, as embattled Afghan security forces struggle to beat back the resurgent Taliban.

The deployment of some 300 Marines to the poppy-growing southern province came one day after the militants announced the launch of their "spring offensive," and as the Trump administration seeks to craft a new strategy in Afghanistan.

Commander of US and NATO forces in Afghanistan General John Nicholson attended a handover ceremony marking the return of the prestigious force, the first Marines in Afghanistan since 2014, an AFP photographer said.

Part of a regular troop rotation announced in January under the Obama administration, they will arrive in stages, eventually numbering some 300 who will take part in NATO's train, assist and advise mission.

Helmand for years was the centerpiece of the US and British military intervention in Afghanistan — only for it to slip deeper into a quagmire of instability.

The Taliban effectively control or contest 10 of Helmand's 14 districts, blighted by a huge opium harvest that helps fund the insurgency.

Around 30,000 people fled fighting in the province in 2016, mostly seeking refuge in provincial capital Lashkar Gah, with the city at times practically besieged.

The US has some 8,400 troops in Afghanistan with about another 5,000 from NATO allies, mostly taking part in the training mission.

Pentagon chief Jim Mattis warned of "another tough year" in Afghanistan when he visited Kabul this week as part of the Trump administration's review of Afghan policy. Nicholson has called for a few thousand more troops to help break the "stalemate".

Mirza Mohammad Yarmand, a retired Afghan general based in Kabul, was optimistic.

"If the Afghan forces and the US Marines jointly fight the phenomenon of the terrorism in southern Helmand, we will have tangible results," he told AFP.

'Butcher of Kabul' returns

The Helmand ceremony came as one of Afghanistan's most notorious warlords, ex-prime minister Gulbuddin Hekmatyar, returned to public life Saturday after more than 20 years in exile.

Hekmatyar, white-bearded and clad in his trademark black turban, called on the Taliban to lay down their weapons and join a "caravan of peace" as he spoke at a rally in Laghman province.

Known widely as the "Butcher of Kabul," Hekmatyar is chiefly remembered for his role in the bloody civil war of the 1990s, in which he stands accused of killing thousands of people in the capital Kabul. He is set to return there on Sunday.

A prominent anti-Soviet commander in the 1980s, his comeback following a landmark peace agreement with President Ashraf Ghani in September has been hugely controversial in Afghanistan, sparking revulsion from human rights groups and residents of the capital.

Hekmatyar called Saturday for a unified Afghan solution to the country's nearly four decades of conflict.

Afghanistan has seen intensified Taliban attacks across the country, leaving Afghan forces — already beset by killings, desertions, and vacuums in leadership and morale — stretched on multiple fronts and facing soaring casualties.

Last week the Taliban delivered a stinging blow as militants dressed in Afghan army uniforms slaughtered at least 135 young recruits at a northern base, according to official figures — though multiple sources say the death toll is much higher.

The attack is believed to be the deadliest by the Taliban on a military target since they were driven from power in 2001. The group vowed more in the statement announcing their so-called "spring offensive" Friday.

With more than one third of Afghanistan outside of government control, civilians also continue to bear a heavy brunt, with thousands killed and wounded each year, including a disproportionate number of children, according to UN figures.

The Marines were among the first US forces sent to Afghanistan after the 2001 terror attacks in the United States.

Several thousand were deployed in Helmand, the deadliest province for US and British forces, where they engaged in bitter combat with the Taliban insurgency.

The US is also targeting Islamic State's affiliate in Afghanistan, earlier this month dropping its largest non-nuclear bomb on the jihadist group's hideouts.

The strike sparked questions over its use against a group that is not considered as big a threat as the Taliban.

Two US troops were killed Wednesday while fighting IS militants near the blast-site in eastern Nangarhar province in an incident potentially involving friendly fire, the Pentagon has said, adding an investigation has been launched.